The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Solenoid actuated valves are known which rely on a solenoid connected by a driving device to reposition a fluid valve member. An electrical current flow to the solenoid creates a magnetic field which displaces the driving device to reposition the valve member from a first to a second position. Removal of the electrical current can cause the driving device to stop in place. A biasing element such as a spring is therefore commonly provided with the valve member which biases the valve member and the driving device opposite to the magnetic field driving direction to automatically return the valve member and the driving device to the non-energized position. Solenoid actuated valves can be used for both normally open and normally closed valves defined when the solenoid is de-energized.
In place of a biasing element, valve assemblies using two oppositely positioned solenoid pilot valves which are individually energized to alternately position the main valve member in each of an open and a closed position are also known. One application of this type of valve is a directional control valve used in bulk material (such as coal) carrying railway cars. The pilot valves are separately energized to each of isolate and permit flow of a pneumatic fluid to control a main pneumatic valve which controls the dump door(s) of the railway car. In arrangements when air pressure can be always present at the main valve, acceleration forces due to car movement, coupling/de-coupling, etc. could cause a main valve to displace when the pilot valves are de-energized, resulting in an unintentional release of the bulk material. A magnet is therefore known in certain applications of these valves which holds the valve member of the main valve closed when the pilot valves are de-energized to prevent unintentional displacement. The magnet, however, is also susceptible to release under certain anticipated acceleration forces. A modified solenoid actuated valve is therefore desirable which eliminates the magnet and provides a positive force in place of the magnet to retain the valve in the closed position.